This disclosure relates to polyester compositions, method of manufacture of the compositions, and articles thereof.
Thermoplastic polyester compositions, such as poly(alkylene terephthalates), have valuable characteristics including strength, toughness, high gloss, and solvent resistance. Polyesters therefore have utility as materials for a wide range of applications, from automotive parts to electric and electronic appliances. Because of their wide use, particularly in electronic applications, it is desirable to provide flame retardancy to polyesters.
Numerous flame retardants (FR) for polyesters are known, but many contain halogens, usually chlorine and/or bromine. Halogenated flame retardant agents are less desirable because of the increasing demand for ecologically friendly ingredients. Halogen-free flame-retardants, such as phosphorus- and nitrogen-based compounds can be used as well. Unfortunately, it can be difficult to achieve excellent flame retardancy in very thin sections.
More ecologically compatible flame retardant (eco-FR) formulations based on aluminum salts of phosphinic or diphosphinic acid compounds and melamine compounds have been developed to overcome environmental issues of halogenated flame retardants. However, these eco-FR compositions can have reduced impact strength and tensile strength, as well as less desirable flow properties compared to compositions having halogenated flame retardants. The addition of small amounts of a polyetherimide (PEI), in particular ULTEM 1010 from Sabic Innovative Plastics, has boosted the mechanical properties of the eco-FR compositions. However, in some circumstances PEI lowers the comparative tracking index (CTI) compared to halogenated frame retardants, i.e., the presence of PEI can increase the tendency to form conductive leakage paths on the surface of a molded article.
Thus, there remains a need for eco-FR thermoplastic polyester compositions having good flame retardant properties and comparable or improved mechanical properties, including ductility, flexural strength, CTI, and stiffness relative to compositions comprising halogenated flame retardants and eco-FR compositions comprising PEI.